SHA-512 Smaller Improvement Suggestions

[Patater]

Description

During review of the PR that added a smaller SHA-512 option, a few improvements were suggested. The PR was merged without these improvements being made, but we should track implementing them to get a few more savings.

• New config.h option to make SHA-512 smaller #178 (comment)
• New config.h option to make SHA-512 smaller #178 (comment)

Issue request type

[ ] Question
[X] Enhancement
[ ] Bug

[ciarmcom]

Internal Jira reference: https://jira.arm.com/browse/IOTCRYPT-884

[adbridge]

Apologies, this was closed in error by the automated bot - re-opening.